Prince Andrew's swearing is classic blue-blooded behaviour

Reports from an American diplomatic source that Prince Andrew is "foul-mouthed" aren't surprising.

The upper classes – at the devil-may-care, I'm-too-grand-for-dreary-politeness end of the spectrum – are fantastically keen on swearwords; the ruder the better.

But they're very good at tailoring them to the occasion: among friends – swear like crazy; in public, on tree-planting, plaque-unveiling occasions, cut out the blue material.

Even the more raffish members of the Royal Family – Prince Philip, the Duchess of Cornwall, Prince Harry – follow the code. What happens in St James's Palace stays in St James's Palace. If you do break into bad language in public, then it's measured bad language – like Princess Anne's "naff off" – an odd form of words, rarely appearing in the most popular swearwords in the English lexicon.

Silly of Prince Andrew to break the code with this sort of show-off swearing. Swear like a trooper in front of your pals, by all means, but not when you're on parade.